The underlying thrust of this proposal is to develop a strategic design system for rationally engineering selective modulators of the immune response. The work proposed here is driven by the hypothesis that small molecules can be designed (based on the known three-dimensional structure of a protein) to inhibit the protein clustering around the T cell antigen receptor that occurs upon the activation of a T cell. Moreover, such compound would only exert its effect on the activated set of T cells (as opposed to resting cells) by inducing functional anergy or apoptosis. Based on this hypothesis, several rationally designed analogs were engineered as mimetics of the alpha chain of CD8. These analogs inhibit CD8+ cytotoxic T cell responses both in vitro and in vivo. The basic tenets of the hypothesis outlined above, have never been tested. The three specific aims of this proposal are designed to test the basic concepts of this rational design strategy. The first aim examines the inhibitory effects of the designed analogs relative to the activity of an anti-CD8 monoclonal antibody in a well-defined CD8+ T cell hybridoma system. The second aim will use the newly developed tetramer staining system for analyzing anti-influenza responses in C57BL/6 mice. Within this system, the analogs will be probed for their ability to induce functional anergy or apoptosis as well as for their effect on secondary T cells. The final aim of the proposal looks at the effects o early treatment with the inhibitory analogs, testing the idea that the analogs will only affect activated cells. The second part of this aim is designed to examine the duration of the in vivo inhibitory response. Once treated how long does the inhibitory period last and when can the animal begin to develop normal immune responses again. Thus, the proposal will test the strategic concepts upon which the rationally designed inhibitors were built. If successful, this may offer a new means of rationally designing drugs that can be used to treat a wide variety of autoimmune diseases as well as to treat the complications that arise from transplantation procedures.